Official fuel consumption

[Kickstart68]

Hi

Reminded by the thread on dynos, my understanding of official fuel consumption figures (and the related emissions figures used to hammer us with tax) is that they are taken from runs on dynos for consistency.

However 2 of the main things that will affect it are weight and aerodynamic drag, neither of which will make the slightest difference to a dyno reading.

Anyone know how these are factored in (pretty safe assumption they are not just ignored)?

As an aside, I presume the max speed of 120kmh / 75mph used for the tests is why some cars spoilers only raise above that figure escaping any penalty from the increased drag.

All the best

Keith

[otolith]

The dyno resistance is set using an empirical measurement of road load. That is done, I believe, to this standard -

http://www.iso.org/iso/iso_catalogue/catalogue_tc/...

Edit - here you go, section 6.1. Total road load power determination

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?...

Edited by otolith on Tuesday 18th October 12:27

[Kickstart68]

Hi

Interesting. Cheers.

Does seem a bit open to fiddles. Seems to measure resistance based on time to decelerate and mass which could be fudged with clever aerodynamics (or not that cleverly, by having spoilers that fold out of the way when in neutral).

All the best

Keith